Reversible step motor



April 10, 1951 H C, LEHDE 2,548,731

REVERSIBLE STEP MOTOR y Filed Nov. 18. 1949 Patented Apr. 10, 1951UNITED STATES PATENT OFFICE REVERSIBLE STEP MOTOR Henry C. Lehde,Brooklyn, N. Y., assignor to Control Instrument Company, Inc., Brooklyn,N. Y., a corporation of New York Application November 18, 1949, SerialNo. 128,223

6 Claims. i

This invention relates to improvements in means for producing rotarymotion, and has particular reference to a means to produce said motionin discrete steps.

Various methods of producing constant increments of angular rotationhave been proposed, some of which, because or" the manner in which therotation is generated, are unsuitable in that the increments of rotationare not constant, and others which produce a constant angular incrementof motion are unsuitable, because they are not reversible.

In the present system, it is proposed to produce a constant increment ofa shafts rotation in response to a single pulse of direct current,regardless of the duration of the pulse and determined in direction bythe pulse polarity. It is also further proposed that each increment ofrotation shall be as nearly the same in angular measurement as theother.

The inventive idea involved is capable of receiving a variety ofexpressions, one of which, for the purpose of illustration, is shown inthe accompanying drawing and described in the specification to follow;but it is to be expressly understood that the drawing and speciiicationare utilized only to facilitate the description of the invention as awhole and not to define the limits thereof, reference being made to theappended claims for that purpose.

The drawing is an isometric View embodying the features ofloi-directional incremental rotations of constant magnitude.

As may be seen in the drawing, the mechanism comprises a yoke VI ofmagnetic metal, energized by a coil 2, which by way of the leads 3 and 4may be connected, through the reversing switch 3|, to a source of directcurrent 32 at the terminals 5 and 6. The yoke I is provided with thepole tip pairs la, 'Ib and 8a, 8b which pole tips, when said yoke isenergized by successive closures of the switch 33, will produce amagnetic field Whose direction will be determined entirely by thedirection of ow of the current in said coil 2.

The pole tips la, 'Ib and 8a, 8b are so constructed as to provide acircular aperture within which a permanent magnet 9 may rotate. Thispermanent magnet is affixed to a shaft I which is supported by thebearing and supporting plate II and is so oriented that it lies in thespace between and, when energized, in the field produced by the poletips. The shaft I0 supports a crank I2 which carries the pin I3 betweenthe pair of opposed, bell crank-shaped floating leversV I4 and I5 whichare free to rotate on the shaft IB but which are restrained from motionalong the shaft. A fixed pin I6 is supported by the plate II which isalso positioned between the oating levers I4 and I5, and a spring I'Iconnects the lower ends of the floating levers Id and I5 so that, inscissors fashion, they are urged to stop against the xed pin I6 and toposition the pin I3 directly thereabove.

In positioning the pin I3, the crank I2 urged thereby will cause theshaft II) to be rotated, and thus will position magnet 9 midway betweenpole tips, this being the position in which said members are shown inthe drawing.

A flow of current through coil 2 will cause the pole tips to becomemagnetized and, depending upon Whether the tips are of one polarity orthe other, the permanent magnet will rotate clockwise, orcounterclockwise, through the small angle necessary for it to alignitself so that ity presents a pole of opposite polarity to the en-Aergized pole tips. Let us suppose that the tips'- i la, 'Ib are madenorth poles and the tips tu, 8h

are made south poles by current flowing in the` coil 2 when the terminal5 is made positive and terminal 6 negative; the permanent magnet 9having poles, as labeled in the drawing, will turn, as seen in thedrawing, counterclockwise, so thatl it will align itself with the tipslb and 8a.. li" the direction of current and the coil 2 were reversed bymaking the terminal 5 negative and terminal 6 positive then the tips la,'Ib would be south poles, the tips 8a, 8b north poles and the permanentmagnet 9 will rotate clockwise to position itself in line with the poletips la and 8b. In either event, the crank I2 and thecrank pin I3 wouldbe carried along with the shaft IB, and the said pin would displace the:lever Iii in the case of a counterclockwise rota-- tion or the lever I5in the case or a clockwise rotation. The remaining lever would be heldby the fixed pin I5, and the motion would stretch the spring II. Whenthe current ceases to flow, the force of the spring Il, tending to closethe levers I4 and I5, will apply a torque by way of the pin I3 and thecrank I2 to the shaft IEB, and return the magnet 9 to its rest positionmidway between the de-energized pole tips.

A-yoke I8 is attached to the other end of the shaft I5 and positioned torotate about a coil I9 which coil is supported by legs on the supportingplate II. Coil I9, when energized, is in parallel with the coil 2, andregardless of the polarity of the applied voltage, Will become magneticand thus attract the clutch plate 20.

' The clutch plate 20 is attached to the ange 2l by means of the pins 22which are freely slidable through said flange and said plate is urged toposition itself against said flange by the clutch springs 23 which actto pull said pins through said plate. When coil it is energized itbecomes magnetic, since the clutch plate 2e is made of a magneticmaterial, and will attract the said clutch plate against the effort ofthe springs 23. The yoke IB projects beyond the coil i9 so that theclutch plate is picked up by the yoke IB before it can come in contactwith coil i9 so that any rotation imparted to the magnet 9 by theenergization of the coil 2 simultaneously with the energization of coilI9 with which it is in parallel, will be imparted to the clutch plate Zand, therefore, to the flange 2 l.

The flange 2l is made fast to the shaft 2Q which terminates in a toothedwheel of soft iron. rhe toothed wheel 25 rotates in the eld of twooppositely poled permanent magnets, or the opposite poles of a singlemagnet, which poles have been slotted so that they present to thetoothed wheel teeth and slots of corresponding size to the teeth andslots of the wheel. Since the reluctance of the gap will be a minimumonly when the teeth of the wheel 25 are in line with the teeth of themagnetic poles 26 and 2l, the shaft 24 will be able to stop only whenthe magnetic path through the gap has a minimum reluctance, and theshaft will be turned upon the release of the clutch 2@ so that, actingin the nature of a detent, there will be discrete positions which theWheel 25 and, therefore, the shaft 2d can occupy and no others.

Shaft 24 carries a worm gear 26 which is in mesh with the worm wheel 2Qcausing the rotation of the shaft 3E), and any rotation imparted to theshaft 2i will, by way of said worm 28 and wheel 2S, be imparted to theshaft til. Since the shaft 2t is constrained bythe detent f5 to discreteincrements of rotation, in like manner the shaft i will produce likeincrements of rotation which are related in magnitude to the motions ofshaft 2li by the gear ratio of the worm and wheel 28 and 2Q on the shaft36.

A pulse of current applied to the terminals 5 and 6 by the switch 33,regardless of its direction, will produce but one step of rotation ofthe shafts 2e and Sii, and if the angle through which the magnet 9 mayrotate corresponds to an integral number of teeth on the detent wheel2E, then the increment of rotation will be fixed and reproduceable foreither direction of rotation.

What is claimed is:

1. In a mechanism for producing fixed increments of rotationcorresponding in direction t0 the polarity of an energizing pulse ofcurrent, a magnetic element having a polarized field adapted to beenergized, a polarized rotatable magnetic means positionable in saidfield and having a shaft, a magnetic clutch energized simultaneouslywith the energization of said polarized field, means to so energize saidmagnetic element and said clutch to rotate said shaft, an output shaftcoupled by said clutch to the first named shaft whenever said polarizedfield and said clutch are simultaneously energized, means coasting withsaid outputshaf t to x the magnitude of its rotation in response to eachcurrent pulse, and means for zeroing and for providing a restoringtorque to said polarized means and its shaft.

2. In a mechanism for producing fixed increments of rotationcorresponding in direction to the polarity of energizing pulse ofcurrent, a magnetic element having a polarized field lit adapted to beenergized, a polarized rotatable magnetic means positionable in saidfield and having a shaft, a magnetic clutch energized simultaneouslywith the energization of said polarized field, means to so energize saidmagnetic element and said clutch to rotate said shaft, an output shaftcoupled by said clutch to the nrst named shaft whenever said polarizedfield and said clutch are simultaneously energized, a detent coupled tosaid output shaft and coacting therewith to fix the magnitude of itsrotation in response to each current pulse, and spring urged membersmounted on said shaft for zeroing and providing a restoring torque tosaid polarized means and its shaft.

3. ln a mechanism for producing fixed increments of rotationcorresponding in direction to the polarity of an energizing pulse ofcurrent, a magnetic element having a polarized field adapted to beenergized, a bar magnet rotatable in said eld, a shaft for said barmagnet rotatable therewith and having a neutral position and also aposition corresponding to each of the directions of said magnetic fieldproduced by current puises of opposite polarity, a magnetic clutchadapted for energization simultaneously with the field of said magneticelement, means to so energize said clutch and field to rotate saidshaft, an output shaft coupled by said clutch to the rst named shaftwhenever said clutch and field are simultaneously energized, a detentcoupled to said output shaft and coacting therewith to nx the magnitudeof rotation in response to each current pulse, and spring urged meanscoacting with the first named shaft to provide a restoring torquetherefor and for said bar magnet. Ll. In a mechanism for producing'fixed increments of rotation corresponding in direction to the polarityof an energizing pulse of current, a magnetic element having a polarizedfield adapted to be energized, a bar magnet rotatable in said field, ashaft for said bar magnet rotatable therewith and having a neutralposition and also a position corresponding to each of the directions ofsaid magnetic field produced by current pulses of opposite polarity, amagnetic clutch adapted for energization simultaneously with the fieldof said magnetic element, means to so energize said clutch and eld torotateV said Shaft, an output shaft coupled by said clutch to the firstnamed shaftv whenever said clutch and field are simultaneouslyenergized, a detent coupled to said output shaft and coacting therewithto fix the magnitude of rotation in response to each current pulse,means including a pair of opposed levers rotatable in oppositedirections about the first named shaft, a spring connecting said levers,and a member carried by said rst named shaft and engageable with saidlevers to rotate the same in opposite directions so as to provide a zeroposition and restoring torque to said bar magnet.

5. In a mechanism for producing fixed increments of rotationcorresponding in direction toA the polarity of an energizing pulse ofcurrent, a magnetic element having a polarized eld adapted to beenergized, a bar magnet rotatable in said field, a shaft for said barmagnet rotatable therewith and having a neutralv position and also aposition corresponding to each of the directions of said magnetic eldproduced by current pulses of opposite polarity, a magnetic clutchadapted.

for energization simultaneously with the field of said magnetic element,means to so energize said clutch and eld to rotate said shaft, an outputshaft coupled by said clutch to the first named shaft whenever saidclutch and field are simultaneously energized, means providing discretestable positions to said output shaft, said means comprising a slottedmagnetic pole element and a toothed Wheel coupled to said output shaftand positionable between the poles of said pole element, and means forzeroing and for providing a restoring torque to the first named shaftand said bar magnet.

6. In a mechanism for producing fixed increments of displacementcorresponding in direction to the polarity of an energizing pulse ofcurrent, an element forming a polarized magnetic field adapted to beenergized, a polarized magnetic member displaceable in said field, amagnetic clutch having connection with said magnetic member andsimultaneously energized with said field, means to so energize saidclutch and CITED rEhe following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,603,646 Sperry Oct. 19, 19262,267,606 Goldstine Dec. 23, 1941 2,432,600 Werner et al. Dec. 16, 19472,444,566

Hennessy et al. July 6, 1948

